Dear Mr. Scienceman...

To make a bubble you need a material that, when spread in a thin film, won't pull itself into a tiny drop (like water pulling itself into a bead on a waxed surface). This tendency to pull into a drop is called surface tension, and water has a high surface tension.

Adding a surfactant (SURFaceACTive AgeNT) to water reduces the surface tension so a bubble can form without collapsing itself into a drop. Reducing the surface tension of water also allows the water to mix with oil and grease, which is why surfactants are used for cleaning!